In order to maintain the rotation speed of a rotor and continue flying, a vertical take-off and landing aircraft such as a helicopter must constantly obtain a torque (hereunder, referred to as “utilizable torque”) that is equal to or greater than a torque required to rotate the rotor (hereunder, referred to as “required torque”) from an engine.
In this regard, PTL 1 describes a method that, automatically calculates a motive power necessary for stopping flight of a helicopter as well as the utilizable maximum motive power in a manner that takes into consideration deterioration of a rotor system in the helicopter, deterioration or failure of an engine, and the current atmospheric conditions and flying weight, and displays the values in contrast with each other to the pilot of the helicopter. According to the method described in PTL 1, since the relation between the motive power that is required for stopping flight and the maximum motive power that is currently utilizable is displayed on an indicator, the pilot can determine whether or not it is possible to stop flight of the helicopter. In this case, in PTL 1, a method is described in which the maximum motive power that is currently utilizable is calculated based on operating parameters of the engine by a calculation that uses an engine model or the like.